A fluid dynamic bearing device has features of high-speed rotation, high rotation accuracy, and low noise. In recent years, by making full use of the features, the fluid dynamic bearing device has been preferably used as a bearing device for motors which is mounted in various electric equipment including information equipment, more specifically, as a bearing device for motors, such as a spindle motor of a magnetic disk device such as an HDD, an optical disk device such as a CD-ROM, CD-R/RW, DVD-ROM/RAM, and a magneto-optical disk device such as an MD and MO, a polygon scanner motor of a laser beam printer (LBP), a color wheel motor of a projector, and a fan motor.
As shown in FIG. 13, such a fluid dynamic bearing device has a bearing sleeve 108 made of sintered metal, a shaft member 102 which is inserted in the inner periphery of the bearing sleeve 108 and is relatively rotated with respect to the bearing sleeve 108, and a housing 107 which houses the bearing sleeve 108. The shaft member 102 has a flanged section 102b at an end of a shaft section 102a. A radial bearing gap is formed between an outer peripheral surface of the shaft section 102a and an inner peripheral surface of the bearing sleeve 108. A first thrust bearing gap S1 is formed between one end surface 102b1 of the flanged section 102b and an end surface 108a of the bearing sleeve 108 opposite thereto. A second thrust bearing gap S2 is formed between the other end surface 102b2 of the flanged section 102b and an inner bottom surface of a housing bottom section 107c. At the time of rotation of the shaft member 102, a dynamic pressure action is produced by a lubricating oil filled in the radial bearing gap, the first thrust bearing gap S1, and the second thrust bearing gap S2, thereby rotatably supporting the shaft member 102 in the radial direction and in both the thrust directions. An upper end opening of the housing 107 is sealed by a seal member 110 (Patent Document 1).